Q: How do I enter the Subterra in the Pharos?
A: I believe you have to pass the pharos first, and then you can go down below the first floor by using the elavator next to the Teleport Crystal on Floor 1.
Q: How do I enter the Henne Mines secret areas?
A: You must have 10 espers unlocked. Speak to Geomancer Yugelu in Jahara. he will unlock the path in the henne mines that leads to the final esper, Zodiark.